Conventional magnetic heads typically employ lapping to fabricate structures within the head. For example, lapping is typically used in processing a write transducer. More specifically, after pole formation, lapping may be used to remove a portion of the device to expose the air-bearing surface (ABS). Lapping determines the windage, the length measured from the ABS to the flare point of the pole of the write transducer. The windage, or nose length, is the distance from the ABS at which the angle the sides of the pole make with a plane parallel to the ABS increases. Similarly, lapping may be used in fabricating other structures in a head, such as the read sensor of a conventional read transducer.
In order to control lapping an electronic lapping guide (ELG) is typically used. FIG. 1 depicts a top view of a conventional ELG 10. The conventional ELG 10 is essentially a resistive stripe. Thus, the conventional ELG 10 is coupled with leads 14 and 16 that are used to determine the resistance of the conventional ELG 10. The conventional ELG has a length l from the surface 12 being lapped. As lapping continues, the surface 12 is worn away, and the length of the conventional ELG 10 decreases. As the length is reduced, the resistance of the conventional ELG 10 increases. Using the resistance of the conventional ELG 10, it can be determined when lapping should be terminated.
FIG. 2 is a flow chart depicting a conventional method 30 for performing lapping using the conventional ELG. The conventional method 30 is described in the context of the conventional ELG 10. The resistance of the conventional ELG 10 is measured during lapping of the transducer, via step 32. The current length of the conventional ELG 10 is determined based upon the resistance measured in step 32 and the sheet resistance of the conventional ELG 10, via step 34. The sheet resistance may be determined in a conventional manner using a conventional Van der Pauw pattern (not shown) provided on the substrate on which the magnetic transducer is to be fabricated. The conventional Van der Pauw test pattern is a well known pattern that may be used to determine sheet resistance of a stripe, such as the conventional ELG 10. Thus, after step 34, the length corresponding to a particular measured resistance for the conventional ELG 10 is known. Alternatively, step 34 could simply convert a desired windage to an ELG length and the ELG length to a desired target resistance of the conventional ELG 10.
The lapping is terminated when the resistance of the conventional ELG 10 indicates that the desired length or target resistance of the conventional ELG 10 has been reached, via step 36. Because the conventional ELG 10 and structure, such as a read sensor or pole, both exist on the transducer being lapped, the lengths of the conventional ELG 10 and the structure change with lapping. Consequently, the lengths of the read sensor or pole may also be set in step 36.
Although the conventional method 30 and conventional ELG 10 function, the desired windage or other desired length may not be easily determined for certain structures. For example, FIG. 3 depicts ABS, side, and top views of a conventional perpendicular magnetic recording (PMR) pole 40 that has a trailing edge bevel 42. For simplicity, FIG. 3 is not to scale. The conventional PMR pole 40 also has sidewalls 44 having a reverse angle and flare point 46. Stated differently, the conventional PMR pole 40 has a top wider than its bottom. Because of the combination of the bevel 42 and sidewalls 44, the windage, the track width, and the pole height change as part of the PMR pole 40 is lapped away. Thus, the geometry of the conventional PMR pole 40 make lapping to the desired windage (nl), track width (tw), and pole height (H) challenging. In addition, there are processing variations that occur for the separate processes used in determining the flare point 46, bevel 42, and sidewalls 44. Variations in these processes may cause variations in the shape or location of these features of the conventional PMR pole 40. It would be desirable, therefore, to compensate for these processing variations. Use of the conventional ELG 10 is not sufficient to do so.
Accordingly, what is needed is an improved method for providing and using an ELG in a magnetic transducer.